Conventional athletic shoes include an upper and a sole. The sole is usually manufactured of a material chosen to optimize a particular function of the shoe, for example, cushioning or stiffness. Typically, the sole includes a midsole and an outsole, either of which can include, for example, a cushioning material to protect a wearer's foot and leg. One drawback with conventional shoes is that the wearer has to select a specific shoe to get optimum performance for a specific activity. For example, the wearer has to use one type of shoe for running and another type of shoe for basketball, because one shoe has more cushioning while the other is stiffer for greater support during lateral movement.
Shoes have been designed that attempt to combine and optimize different functions of sport specific shoes; however, the wearer is still left with a shoe with set functionality that the wearer cannot customize. What may be optimal for one segment of the population is not necessarily optimal for everyone. For example, many shoes are designed with wedges or varying degrees of cushioning across the width of the sole to compensate for pronation or supination. Unfortunately, these shoes are typically limited to compensating for either pronation or supination and the amount of compensation cannot be varied to suit a particular wearer. Furthermore, shoes have been designed that attempt to give a wearer some adjustability with respect to a specific function; however, these shoes may require at least partial disassembly of the shoe and/or the wearer may be limited in the amount of adjustment that can be made.
U.S. Pat. No. 5,875,568, the disclosure of which is hereby incorporated herein by reference in its entirety, discloses a cushioning system including a cylindrical shock-absorbing insert located in a heel of a shoe. Similarly, U.S. Pat. Nos. 4,430,810 and 4,573,279, the disclosures of which are hereby incorporated herein by reference in their entireties, also disclose cylindrical inserts located in the heel of the shoe. There are several drawbacks to these cushioning systems. For example, the inserts are isotropic. To adjust the cushioning properties of an isotropic insert, the wearer has to remove the insert and replace the insert with another insert having different cushioning properties. The '568 patent discloses rotating the insert to “renew” the cushioning effect of the insert, but the cushioning effect is the same no matter what orientation is selected. In addition, the inserts can “turn” during use, because there is no mechanism for locking the inserts against rotational movement during use.
There is, therefore, a need for a shoe that the wearer can easily, repeatedly, and securely customize. Such a shoe should give the wearer the ability to make numerous adjustments to the functional characteristics of the shoe, for example, increased cushioning, compensation for pronation, compensation for supination, etc.